The enzyme catalyses the sequential degradation of (1->4)-alpha-D-glucans from the non-reducing end with the release of 1,5-anhydro-D-fructose. Thus, for an alpha-glucan containing n (1->4)-linked glucose units, the final products are 1 glucose plus (n-1) 1,5-anhydro-D-fructose. Maltose, maltosaccharides and amylose are all completely degraded. It does not degrade (1->6)-alpha-glucosidic bonds and thus the degradation of a branched glucan, such as amylopectin or glycogen, will result in the formation of 1,5-anhydro-D-fructose plus a limit dextrin. Other enzymes involved in the anhydrofructose pathway are EC 4.2.1.110 (aldos-2-ulose dehydratase), EC 4.2.1.111 (1,5-anhydro-D-fructose dehydratase) and EC 5.3.2.7 (ascopyrone tautomerase).